1. Field of the Invention
Embodiments of the present invention generally relate to an apparatus and method of deposition utilizing multiple precursors. More particularly, embodiments of the present invention relate to an apparatus and method of cyclical deposition utilizing multiple precursors in which delivery of at least two of the precursors to a substrate structure at least partially overlap.
2. Description of the Related Art
Reliably producing sub-micron and smaller features is one of the key technologies for the next generation of very large scale integration (VLSI) and ultra large scale integration (ULSI) of semiconductor devices. However, as the fringes of circuit technology are pressed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on the processing capabilities. The multilevel interconnects that lie at the heart of this technology require precise processing of high aspect ratio features, such as vias and other interconnects. Reliable formation of these interconnects is very important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates.
As circuit densities increase, the widths of vias, contacts, and other features, as well as the dielectric materials between them, decrease to sub-micron dimensions (e.g., less than 0.20 micrometers or less), whereas the thickness of the dielectric layers remains substantially constant, with the result that the aspect ratios for the features, i.e., their height divided by width, increase. Many traditional deposition processes have difficulty filling sub-micron structures where the aspect ratio exceeds 4:1. Therefore, there is a great amount of ongoing effort being directed at the formation of substantially void-free and seam-free sub-micron features having high aspect ratios.
Atomic layer deposition is one deposition technique being explored for the deposition of material layers over features having high aspect ratios. One example of atomic layer deposition of a binary material layer comprises the sequential introduction of pulses of a first precursor and a second precursor. For instance, one cycle for the sequential introduction of a first precursor and a second precursor may comprise a pulse of the first precursor, followed by a pulse of a purge gas and/or a pump evacuation, followed by a pulse of a second precursor, and followed by a pulse of a purge gas and/or a pump evacuation. Sequential introduction of separate pulses of the first precursor and the second precursor results in the alternating self-limiting chemisorption of monolayers of the precursors on the surface of the substrate and forms a monolayer of the binary material for each cycle. The cycle may be repeated to a desired thickness of the binary material. A pulse of a purge gas and/or a pump evacuation between the pulses of the first precursor and the pulses of the second precursor serves to reduce the likelihood of gas phase reactions of the precursors due to excess amounts of the precursor remaining in the chamber. Therefore, there is a need for an improved apparatus and method of atomic layer deposition utilizing three or more precursors.